Transforming Plastic Waste into Clean Hydrogen

From Shopping Bags to Fuel

Plastic is everywhere—water bottles, grocery bags, car dashboards—and once we toss it, most of it stays tossed. Only about 9 percent of discarded plastic is recycled. The rest piles up in landfills or goes up in smoke, releasing carbon dioxide along the way.

The usual bottleneck is sorting. Different plastics need different treatments, and that labor and cost keep recycling rates stubbornly low. Now a team co-led by researchers at the UCLA Samueli School of Engineering and Ewha Womans University in South Korea has shown a way around the problem: a single chemical process that takes a jumble of the three most common plastics and turns them directly into clean hydrogen fuel.

No sorting required. And the carbon does not escape into the air.

One Reactor, Three Plastics

The method is called alkaline thermal treatment, or ATT. In plain terms, sodium hydroxide—the same compound behind drain cleaners and soap-making—reacts with the plastic under heat and coaxes out hydrogen gas. The team adapted ATT from an earlier approach they had developed to turn biomass such as seaweed into hydrogen in a carbon-neutral way.

In the lab, they fed the reactor polyethylene terephthalate (PET—the clear stuff in water bottles), polyethylene (PE—think shopping bags), and polypropylene (PP—yogurt lids and car parts). The mixture produced hydrogen with purities above 90 percent, and it did so at temperatures 300 to 400 degrees Celsius cooler than traditional steam gasification.

PET was a natural. PE and PP, built entirely of carbon-hydrogen bonds, were more stubborn at first. So the researchers added a gentle warm-up step: a brief thermal oxidation pretreatment in air that introduces oxygen-containing groups along the polymer chains. Those new sites give the alkaline chemistry something to grab onto. Once activated, all three plastics break down efficiently in the same reactor.

Carbon That Stays Put

Here is the part that feels almost magical. As the plastics decompose, the carbon does not fly off as CO₂. The sodium hydroxide captures it and converts it into solid sodium carbonate—a stable mineral. Post-reaction analysis found that more than 75 percent of the original plastic carbon ends up either as that carbonate or as liquid organic residues. Less than 13 percent appears in gaseous form, and direct release of carbon dioxide to the atmosphere during the reaction is negligible.

The sodium carbonate can then be converted, through a simple recovery step, into calcium carbonate—the same mineral used in cement and other industries that have long been hungry for carbon-intensive materials. In effect, yesterday’s packaging becomes today’s mineral feedstock while the hydrogen heads off to power clean energy systems.

“We are solving two urgent global problems at the same time,” said co-corresponding author Ah-Hyung “Alissa” Park, dean of UCLA Samueli and a professor of chemical and biomolecular engineering. “Plastic waste is accumulating at alarming rates, and clean hydrogen is essential for decarbonizing energy. This technology tackles both of these challenges in a creative and scalable way.”

Earlier low-temperature methods, such as solar-driven photoreforming or electrochemical conversion, could handle oxygen-rich plastics like PET but left PE and PP—two of the most abundant plastics in the waste stream—out of reach. High-temperature gasification can take mixed plastics, yet it pours out substantial CO₂. ATT is the first approach from this team that addresses all three limitations at once: mixed waste, lower temperature, and inherent carbon storage.

Next Steps on the Horizon

The researchers are clear-eyed about the path ahead. Further work is needed to optimize the process and to evaluate its economic viability before it can be deployed at scale. That diligence is exactly what turns a promising laboratory result into something that might one day sit beside recycling plants and hydrogen hubs.

Co-corresponding author Woo-Jae Kim of Ewha Womans University sees the bigger picture: by cutting the sorting costs and process complexity that have blocked commercialization, the technology could support both the hydrogen economy and the circular economy.

Imagine a future in which the plastic that once clogged landfills becomes a reliable source of clean fuel, while its carbon is locked into useful minerals instead of warming the sky. The chemistry is already working in a single reactor. The next chapters—scaling, refining, integrating—are the open frontier that makes this moment feel full of possibility.

“By reducing the sorting costs and process complexity that have been major barriers to commercialization, this technology has the potential to become a next-generation core technology that supports both the hydrogen economy and the circular economy.” — Woo-Jae Kim